The present invention relates to a simple optical fiber inner tube connector, and more particularly to an optical fiber inner tube connector that is internally threaded for two optical fiber inner tubes to screw into two ends of the connector and externally provided at two ends with sealing elements to seal two ends of the connector in an airtight manner.
The optical fiber cable is an advanced transmission material for communication line. The optical fiber cable effectively isolates the transmitted signals from noise interference by the electromagnetic wave. The optical fiber cable also has the advantages of high band width and good ability of overcoming the problem of lose of signal and is therefore a good substitute for conventional copper coaxial cable and electric cable. With the optical fiber cable, better signal transmission effect may be achieved over the high-speed telecommunication network.
However, due to its fragility, the optical fiber cable requires more strict external protection than the conventional copper cables. Usually, the optical cable includes an outer tube in which three or four inner tubes with smaller diameter than that of the outer tube are received. Each of the inner tubes has an optical fiber extending therethrough. In other words, each optical fiber cable includes at least two layers of protection separately provided by the outer and the inner tubes. The outer and the inner tubes are basically made of plastic material. Generally, the outer tube is made of hard and wear-resistant plastic material, such as polyvinyl chloride, and the inner tube is made of softer plastic material, such as polyethylene or other plastic material having similar physical property.
In practical installation of the optical fiber cable, the outer tube is first embedded under ground. Thereafter the inner tubes are put into the outer tube. As being limited by the available length of the inner tube and different extending directions of the optical fiber cable, a plurality of segments of the inner tube must be used and connected segment by segment to complete the primary embedding of the optical fiber cable line. Finally, an optical fiber is inserted through each of the inner tubes by means of compressed air. The compressed air brings the optical fiber from one end of the inner tube to the opposite end thereof. To effectively make use of the compressed air in moving the optical fiber through the inner tube, the inner tube must be excellently airtight through the whole length thereof. Therefore, the air-tightness of the inner tube at its connections between two adjacent segments thereof is absolutely required.
In addition to the air-tightness, it is also necessary to actually prevent moisture, insects and other foreign materials from entering into the inner tube via the connections between two segments.
Moreover, in order to provide the connection between the inner tube segments with a sufficient strength to resist unwanted separation of the inner segments from one another, the inner tube segments have to be securely and firmly connected to one another in order to resist any pull or push force applied thereto by the compressed air during installing the optical fiber cable.
To achieve the aforesaid requirement of air-tightness, the currently available conventional connectors for connecting two inner tube segments to each other usually include numerous complicate components and are therefore difficult to handle at the work field. In connecting two inner tube segments to each other, an optical fiber inner tube connector is needed. For an inner tube segment to readily connect to the inner tube connector, a radial clearance is usually provided between the connector and the inner tube segment. However, such radial clearance tends to cause separation of the inner tube segment from the connector due to pull or push force applied on the inner tube segment during work. Moreover, such radial clearance may also cause improper axial alignment between two inner tube segments connected to two ends of the connector. The segments may be radially offset with respect to each other and causes problems in moving the optical fiber through the inner tubes.
U.S. Pat. No. 5,832,158 entitled xe2x80x9cOptical Fiber Inner Tube Connectorxe2x80x9d granted to the applicant and U.S. patent application Ser. No. 09/109,007 entitled xe2x80x9cOptic Fiber Inner Tube Connectorxe2x80x9d filed by the applicant on Jul. 1, 1998 both disclose optical fiber inner tube connectors that are effective in solving the problems existed in the conventional optical fiber inner tube connectors. These connectors are, however, structurally complicate and do not ensure an absolutely trouble-free connection of optical fiber inner tubes to one another.
A primary object of the present invention is to provide a simple optical fiber inner tube connector that enables most convenient connection of two optical fiber inner tubes to one another in the airtight manner.
Another object of the present invention is to provide a simple optical fiber inner tube connector that ensures absolutely sealed connection of two optical fiber inner tubes to effectively prevent moisture, insect and other foreign materials from entering into the inner tubes.
A further object of the present invention is to provide a simple optical fiber inner tube connector that ensures firm connection of two optical fiber inner tubes to one another so that the two inner tubes would not be easily pulled or pushed apart from one another during the installation of the optical fiber cable.
A still further object of the present invention is to provide a simple optical fiber inner tube connector that automatically guides two optical fiber inner tubes to be connected thereto to axially align with each other without being offset relative to each other, and therefore facilitates accurate connection of the inner tubes and subsequent smooth extending of the optical fiber through the connected inner tubes.
To achieve the above and other objects, the simple optical fiber inner tube connector of the present invention mainly includes a tubular body being divided into two receiving chambers by at least an annular rib in the tubular body. Each of the receiving chambers is provided around its inner wall surface with a spirally extended thread and at least an engaging tooth located between the annular rib and an inner end of the spiral thread. When two optical fiber inner tubes are to be connected to each other by means of the connector, they are separately screwed into the two receiving chambers so that the engaging teeth tightly engage into outer wall surfaces of the two optical fiber inner tubes for them to accurately align with each other and firmly locate in the connector. Waterstop sleeve members made of elastically deformable material may be put around outer wall surface of the tubular body near two ends thereof to fitly and tightly cover the joint of the connector and the optical fiber inner tubes and to align center lines of the inner tubes with that of the tubular body.